User Manual

AS4000 Operations and Maintenance
Section
605-0000-431
6
. Issue 1.6. Date3/2/99
DLP-020
Page 46 of 60 © Copyright Airspan Communications Corporation 1999
CRU Characterisation
Each CRU has a characterisation label fixed to the CRU back plate. This label
records factory measured readings of TX PC and RX AGC Volts for different set
levels.
AGC Voltage Measurement
1. Using the DMM, measure the DC voltage between Ground (green) and the AGC
Monitoring point, (red) on the breakout socket.
2. Check the label on the CRU to get an indication of the receive signal strength from
the characterised readings to ensure that the required fade margins are attained; The
higher the voltage the stronger the signal. The reading should indicate a receive
strength greater than -98dBm. If the original test form is available check the value of
the DC voltage against that on the test result sheet.
-98
-92
-88
RECIEVE SIGNAL
STRENGTH /dBm
AGC DIGITAL
VOLTMETER
READING
Figure 1-4. Label Detail: Receive AGC
3. CRU check the label on the CRU to get an indication of the RX signal strength. If
there is any significant difference in AGC voltage from the original reading or the
RX signal strength is less than -98 then check for any obstructions in the path and if
necessary PAN the CRU to improve the RX signal strength.
CRU Panning
1. Using the DMM, Using the DMM, measure the DC voltage between Ground
(green) and the AGC Monitoring point, (red) on the breakout socket. Whilst
observing the voltage on the DMM, pan the CRU through the peak point, then pan
back to it. If there is not sufficient panning range use the other mounting point on
the CRU mounting bracket in order to pan through the peak. Check that the CRU
does not break the CRU positioning criteria as shown in Figure 1-6.